Piaggio Vespa 400

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Vespa 400

1957 - 1961
2 cyl. / 2 stroke
24.0 cu in / 0.4 litres
12 hp / 14 hp
3 spd. man
Top Speed:
50 to 55 mph
Number Built:
4 star
Vespa 400
Reviewed by Unique Cars and Parts
Our Rating: 4

Ateliers de Construction de Motocycles et d'Automobiles

The Vespa 400 was a rear-engined microcar, produced by ACMA (Ateliers de construction de motocycles et d'automobiles) in Fourchambault, France, from 1957 to 1961 to the designs of the Italian Piaggio company. Two different versions were sold, "Lusso" and "Turismo".

The car made its public debut on 26 September 1957 at a press presentation staged in Monaco. The ACMA directors ensured a good attendance from members of the press by also inviting three celebrity racing divers to the Vespa 400 launch. The 400 was a two seater with room behind the seats to accommodate luggage or two small children on an optional cushion.

Everything about the Vespa 400 was simple and practical. It had a roll-back canvas hood similar to the baby Fiats, and its interior layout was also much the same, although there was a little more leg-room, both front and rear. Like the Fiat, it had bucket seats for two adults and a padded bench at the rear with room for two kids or quite a lot of luggage.

The unitary-construction body had a pronounced reinforcing channel running down the middle, which aommodated controls leading to the rear-mounted engine. Finish throughout was plain but attractive. The Vespa 400 was powered by a tiny 393 c.c. two-stroke, air-cooled engine, the air forced by a fan over he finned cylinders, placed in line and inclined at 20 deg. from the vertical to reduce the height of the unit.

The bore and stroke were equal at 63mm., and compression ratio was 6.4-1. Near the end of production the compression ratio was increased respectively to 6.6:1 and 14 hp. Refinements included an oil-bath air-cleaner, twin coils and automatic ignition advance. The engine design was very simple, with every part easily accessible, and the of forced air cooling allowed the makers to provide a ducted heating system as standard.

The three-speeds-and-reverse gearbox had synchromesh on second and third, and was controlled by a well-placed central floor gearshift; a stubby lever-type handbrake was located between the front seats, and there was the normal layout of clutch, brake and accelerator pedal. The brakes were hydraulic, and the suspension was independent on all wheels, by coil springs enclosing long double-acting telescopic shock-absorbers, plus a stabiliser bar at the front.

The front-end layout was unusual in that the shock-absorbers served as part of the steering system, transferring the commands of the high-placed rack-and-pinion steering to the wheels. The rack actually sat above the driver's shins - Vespa put it there to allow maximum leg-room. With a dry weight of only 53 lb., Vespa claimed a top speed of 55 m.p.h., a cruising speed very near the limit, and fuel economy of 60 m.p.g. This should have meant it had a range of about 270 miles with the 4.5-gallon petrol tank, mounted left of engine.

The length of the Vespa 400 was 9ft. 4in., width 4ft. 2 in.; height 4ft. 1in. (empty). It had a wheelbase of 5ft. 6|in. and front and rear track equal at 3ft. 7.5in., and it had a turning circle of only 24.5 feet. The front seats were simple tubular metal frames with cloth upholstery on elastic "springs" and between the seats were the handbrake, starter and choke. The gear change was centrally floor mounted. The rear hinged doors were coated on the inside with only a thin plastic lining attached to the metal door panel skin allowing valuable extra internal space. On the early cars the main door windows did not open which attracted criticism, but increased the usable width for the driver and passenger.

Instrumentation was very basic with only a speedometer and warning lights for low fuel, main beam, dynamo charging and indicators. The cabriolet fabric roof could be rolled back from the windscreen header rail to the top of the rear engine cover leaving conventional metal sides above the doors. The 12 volt battery was located at the front of the car, behind the dummy front grill, on a shelf that could be slid out. The spare wheel was stowed in a well under the passenger seat.

Behind the wheel, the Vespa 400's steering was light, exceptionally direct, and with very little self-centring effect. The all-independent suspension gave an excellent ride at any speed, and most corners could be taken with the foot hard down. The little gearshift was also a delight to use. The two-stroke engine was noisy when idling but quietened down as you got moving; at around 45-50 m.p.h. noise level was surprisingly low. The seating was on the hard side, and while cute these days, for every day use rear-hinged doors and fixed windows were not great. Juan Manuel Fangio even took a Vespa 400 over the French Alps and along the winding coastal roads of the Riviera a few days before the car was released. His comment: "It was so comfortable that I felt I was driving a much bigger car."
Vespa 400

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